We will be investigating; 1) The function and cellular processing of prepro-EGF in the kidney. Using antisera against EGF and the amino- and the carboxyl terminals of prepro-EGF, the cellular processing of prepro-EGF will be studied by light and electron microscopic immunocytochemistry in combination with pluse-chase immunoprecipitation. EGF receptors (EGF-R) will be identified in the kidney and urinary tract using 125I EGF for autoradiography and EGF-R synthesis studies by in situ hybridization with an EGF-R cRNA probe. These studies will test the hypothesis that prepro-EGF functions in the kidney as a membrane-spanning protein, acting as a receptor for a putative ligand in the tubular fluid. In doing so, prepro-EGF may release EGF to bind with EGF-R in the urinary tract downstream, where it may have a trophic effect. 2) Immunoelectron microscopy of intracellular renin maturation in the JGA. We intend to analyze the intracellular distribution of renin and pro-renin and their relationship to acidic sites in the JG cell using immuno-gold labeling at the ultrastructural level. These studies are related to renin-dependent forms of hypertension. 3) The development of the afferent and efferent rental innervation. These developmental studies will use silver impregnations, peroxidase transport, catecholamine fluorescence and electron microscopy. b) The relationship between NGF and the development of renal innervation. Using immunocytochemistry and in situ hybridization, the site of NGF localization and its synthesis will be correlated with the onset of renal innervation in the developing mouse and rat. c) NGF in the kidney of the spontaneously hypertensive rat (SHR). The onset and timing of NGF synthesis in the developing SHR and normotensive rat will be investigated with in situ hybridization. The SHR is widely used as a model for human hypertension.